In the known art, the mounting arrangement of the blades on the hub of a wind turbine is generally based on ball or rolling bearings for the transmission of the involved axial forces and flexural moments.
Said axial forces and flexural moments depend on many factors and in particular the features and dimension of the blades, the wind velocity and the pitch system used for regulating the pitch of the blades.
U.S. Pat. No. 6,799,947 B2 discloses a bearing for an adjustable rotor blade for a wind turbine having an axial-type pitch system comprising a bearing race for the one co-operating bearing component, which bearing race receives in positively locking relationship two radially mutually displaced rows of rolling bodies, and a bearing race for the other co-operating bearing component, which embraces them in a U-shape in cross-section, wherein the bearing race for the rotor blade forming the other co-operating bearing component comprises two rings of different diameters which are fixed independently of each other to the rotor blade. That arrangement affords on the one hand a practically three-race rolling bearing whose central race which is secured to the other co-operating bearing component, upon the occurrence of flexural moments (and axial forces) receives from the two outer races (or race portions of the embracing bearing race) pressure forces in directions which extend more or less perpendicularly to each other and which are thereby automatically rendered symmetrical, and the pressure forces therefore respectively remain in the central region of the bearing raceway quadrants, while on the other hand the forces from the rotor blade are simultaneously applied to the two outer races (or race portions) and this therefore provides for more uniform loading of the mounting and the rotor blade root.
In wind turbines having pitch control systems based on lineal actuators such as the system disclosed in EP 1 126 163 A1 the blade bearings are generally single or double race bearings such as the illustrated in particular in FIG. 1 of said document. The outer ring of these bearings can have a large deflection and thereby a poor load distribution. This invention is intended to solve this drawback.